Information retrieval is the science of searching for information in documents, searching for documents themselves, searching for metadata which describes documents, or searching within databases, whether relational standalone databases or hyper textually linked databases, such as the World Wide Web. Automated information retrieval systems are typically used to reduce information overload. Many universities and public libraries use information retrieval systems to provide access to books, journals, and other documents. Web search engines (e.g., Live Search) also use information retrieval techniques and are one of the most visible and commonly utilized manifestations of an information retrieval application.
An information retrieval process typically begins when the user enters a query into an information retrieval system. Queries are typically formal statements of information need, for example, search strings in web search engines. In information retrieval a query does not necessarily uniquely identify a single object in the collection; rather several objects may match the query, perhaps with different degrees of relevancy.
An object can be an entity that keeps or stores information in a database, for instance. User queries can thereafter be matched to the objects stored in the database where, depending on the application, the data objects can be, for example, text documents, images, or videos. In order to facilitate efficient query matching, most information retrieval systems compute a numeric score reflecting how well each object in the database matches the query, and ranks the objects according to this value or in combination with other information. The top ranking objects can then be shown to the user and the process can be iterated should the user wish to further refine the query.